1. Field of the Invention
The present invention relates to a video interface mechanism used when an image is displayed on a display panel, more particularly to a method of driving a plurality of display panels or a high-resolution panel, a driving device for driving the same, a display device and the like.
2. Related Art
Recently, a technology has been proposed, in which a plurality of display panels are connected to a host system such as a personal computer (hereinafter, referred to as PC) and the plurality of display panels are used as a display device constituting a large screen as a whole. At this time, according to an ordinary video interface specification, to transfer an image, one graphics controller is required for one display. For example, when it is tried to display respectively different images on four display panels, four video chips are necessary. For this reason, even though it is tried to allow a large number of display panels to display images with an ordinary video interface, there is a limitation on the number of graphics controllers that can be loaded on a PC, that is, on the number of display devices that can be connected to a PC. Only four to eight display panels at most can be connected to a PC. Accordingly, there is naturally a limitation on extension of the display panel.
Furthermore, a resolution of the display panel itself has recently advanced, and as high-resolution (ultra high-resolution) panels, such as a QXGA (Quad Extended Graphics Array) panel (2048×1536 dots) and a QUXGA (Quad Ultra Extended Graphics Array) panel (3200×2400 dots) are being put into practical use. However, system power and graphics chip power come to be incapable of following the advancement of the panel, and a sufficient display cannot be actually performed with an ultra high-resolution panel. Accordingly, as means for solving power deficiency of the graphics chip, a method in which a memory is provided on a display device side and a transfer rate is dropped to an extent that can be realized technically is conceived. However, the method cannot cope with a moving picture display and the like which require a high transfer rate. On the other hand, in order to cope with such a high-resolution display, a method in which a screen is divided and the divided screens are processed individually by a plurality of driving mechanisms is conceived. However, also in this method, in spite of existence of one panel, a host system must execute the same processing as that executed when a plurality of panels exist. Accordingly, for the similar reason to the case of the connection of the plurality of panels, an extension of the processing has been difficult.
In order to solve such problems, a technology to connect display panels in a cascade connection is proposed in Japanese Patent Laid-Open No. 11-164354. This technology adds a control signal after information of the lowermost line in the video signals of a frame, thus realizing a multi-panel in the form of a daisy chain. According to this technology, an enlarged display using a plurality of display devices in a cascade connection is enabled by a simple modification of software without a modification of hardware on the system side.
On the other hand, according to Japanese Patent Laid-Open No. 11-164354, a control signal is sent out to each panel from a host system side via a video signal line. For this reason, it is sometimes required for the host system side to execute processing relatively strongly conscious that a screen is divided into plural pieces. Moreover, in the case of the cascade connection of the panels in the foregoing application, a technical problem concerning signal deterioration due to relays of signal through the panels is left.
In the foregoing technologies, the number of panels connected is limited. At the same time, when it is tried to realize a multi-panel environment, it is difficult to execute the same operation depending on the number of panels connected. To be more specific, although it is tried to realize the multi-panel environment, there are serious limitations to the number of panels connected and a connection thereof. Moreover, it is impossible to execute any type of multi-panel application.